<template>
  <div>
    <h1>当前求和为:{{sum}}</h1>
    <select v-model.number="n">
      <option :value="1">1</option>
      <option :value="2">2</option>
      <option :value="3">3</option>
    </select>
    <button @click="increment">+</button>
    <button @click="decrement">-</button>
    <button @click="incrementOdd">当前求和为奇数再加</button>
    <button @click="incrementWait">等一等再加</button>
  </div>
</template>
<script>
export default {
  name: 'Count',
  data() {
    return {
      n: 1, //用户选的数字
      sum: 0 //当前的和
    };
  },
  methods: {
    increment() {
      this.sum += this.n;
    },
    decrement() {
      this.sum -= this.n;
    },
    incrementOdd() {
      if (this.sum % 2) {
        this.sum += this.n;
      }
    },
    incrementWait() {
      setTimeout(() => {
        this.sum += this.n;
      }, 500);
    }
  }
};
</script>
<style lang="less" rel="stylesheet/less" scoped>
</style>